An herbicide is a compound which adversely controls or modifies plant growth, e.g., killing, retarding, defoliating, desiccating, regulating, stunting, tillering, stimulating, and dwarfing. The term "plant" refers to all physical parts of a plant, including seeds, seedlings, saplings, roots, tubers, stems, stalks, foliage, and fruits. "Plant growth" includes all phases of development from seed germination to natural or induced cessation of life.
Herbicides are generally used to control or eradicate weed pests. They have gained a high degree of commercial success because it has been shown that such control can increase crop yield and reduce harvesting costs.
The most popular methods of herbicide application include: pre-plant incorporation into the soil; in-furrow application to seeds and surrounding soil; pre-emergence surface treatment of seeded soil; and post-emergence treatment of the plant and soil.
A manufacturer of an herbicide generally recommends a range of application rates and concentrations calculated to maximize weed control. The range of rates varies from approximately 0.01 to 50 pounds per acre (0.0112 to 56 kilograms per hectare (k/ha)), and is usually in the range of from 0.1 to 25 pounds per acre (0.112 to 28 k/ha). The term "herbicidally effective amount" describes the amount of an herbicide compound which controls or modifies plant growth. The actual amount used depends upon several considerations, including particular weed susceptibility and overall cost limitations.
The most important factor influencing the usefulness of a given herbicide is its selectivity towards crops. In some cases, a beneficial crop is suceptible to the effects of the herbicide. In addition, certain herbicidal compounds are phytotoxic to some weed species but not to others. To be effective, an herbicide must cause minimal damage (preferably no damage) to the beneficial crop while maximizing damage to weed species which plague that crop.
Depending on the particular formulation used, the pyrrolidone herbicide compounds of this invention have either of two different effects on crops and weeds. When a pyrrolidone compound is formulated as an emulsifiable concentrate and applied, bleaching of the crop occurs in the early stages of growth. Bleaching is due to loss of pigmentation in a plant and is seen as a yellowing of the plant's leaves.
When a pyrrolidone compound is formulated as a microcapsule, bleaching of the crop is significantly lessened. However, weed control is also reduced.
To preserve the beneficial aspects of herbicide use, i.e., to maximize weed control, and to minimize crop damage, many herbicide antidotes have been prepared. These antidotes reduce or eliminate damage to the crop while maintaining or increasing the damaging effect of the herbicide on weed species; See, for example, U.S. Pat. Nos. 3,959,304; 4,021,224 and 4,021,229 and Belgian Pat. No. 846,894.
The precise mechanism by which an antidote reduces herbicidal crop injury has not been established. An antidote compound may be a remedy, interferent, protectant, or antagonist. As used herein, "antidote" describes a compound which has the effect of establishing herbicide selectivity, i.e., continued herbicidal phytotoxicity to weed species and reduced or non-phytotoxicity to cultivated crop species. The term "antidotally effective amount" describes the amount of an antidote compound which counteracts a phytotoxic response of a beneficial crop to an herbicide.